Polyethyleneimine modified carbohydrate doped thin film composite nanofiltration membrane for purification of drinking water

A green method for safety drinking water production was proposed in this study by the development of a positively charged nanofiltration (PNF) membrane composed of two different functional layers. Glycosyl layer was fabricated through interfacial polymerization in which the performances of sucrose doped NF membrane was superior to the glucose and raffinose doped membranes, which were further enhanced by alkali treatment. Sucrose (0.8 wt%) and NaOH (0.05 mol‧L −1 ) benefit the formation of higher porosity and better hydrophilicity and offer a high pure water flux (13.5 L m −2  h −1 ·bar −1 ) and Na 2 SO 4 rejection (99.3%). Then, the PNF membrane was acquired by coating polyethyleneimine (PEI) on the sucrose-polyamide layer. The concentration of PEI and grafting time were both studied and the optimal membrane showed an excellent performance for heavy metals removal . The as-developed membrane has found its potential application in drinking water purification which gave 90% rejection for heavy metals and the permeance reached to 7.4 L m −2  h −1 ·bar −1 . With the proposed method, the trace elements were retained partially which was beneficial to the human body and the toxic metals were kept within the limits.